Various devices can be installed in a well traversing a hydrocarbon-bearing subterranean formation. Some devices control the flow rate of fluid between the formation and tubing, such as production or injection tubing. An example of these devices is an autonomous fluid selector that can select fluid, or otherwise control the flow rate of various fluids into the tubing.
An autonomous fluid selector can select between wanted and unwanted fluids based on relative viscosity of the fluids. For example, fluid having a higher concentration of unwanted fluids (e.g. water and natural gas) may have a certain viscosity in response to which the autonomous fluid selector directs the unwanted fluid in a direction to restrict the flow rate of the unwanted fluid into tubing. The autonomous fluid selector includes a flow ratio control assembly and a vortex assembly usable to select fluid based on viscosity. The flow ratio control assembly includes two flow paths. Each flow path includes narrowed conduits that are configured to restrict fluid flow based on viscosity of the fluid. For example, one conduit in the first passageway may be narrower than the second conduit in the second passageway, and configured to restrict fluid having a certain relative viscosity more than fluid having a different relative viscosity. The second conduit may offer relatively constant resistance to fluid, regardless of the viscosity of the fluid.
Although this autonomous fluid selector is very effective in meeting desired fluid selection downhole, additional types of autonomous fluid selectors are desirable that can direct fluid for flow control based on small differences in fluid properties.